There are many portable generators available that allow for an remote start. The problem is they are mostly louder generators, not the nice quiet inverter models. Most of Honda's entire line, for instance, has this feature. You'll need the matching wiring harness and probably a generator controller. Portables often use a 3 wire start system of which there are 2 different versions. They are unlike home generators that usually use a 2 wire start system. (of which there are also 2 versions).
Magnum energy makes a decent stand-alone Automatic Generator Start (AGS). If you happen to already have a Magnum inverter in your RV then you can use the network AGS. Schneider conext makes an AGS too but it will not operate "stand alone". But, again, if you happen to have a Schneider/Conext/Trace/Xantrex inverter in your RV you could use it.
There are other companies that make stand alone AGS boxes but I haven't had good luck with them in the past.
